Regulator Control Integrated Circuit Having COT and Valley Current Modes

ABSTRACT

A voltage regulator control integrated circuit includes constituent parts including an error amplifier circuit, a comparator circuit, a compensation signal generator circuit, an oscillator/one-shot circuit, a latch, and a current sense circuit. In a first example, the integrated circuit is operable in a first mode and in a second mode. In the first mode, the various parts are configured and interconnected in such a way that they operate together as a valley current mode regulator control circuit. In the second mode, the various parts are configured and interconnected in such a way that they operate together as a current-mode constant on-time mode regulator control circuit. In another example, a voltage regulator control integrated circuit has the same basic constituent parts and is operable in a first mode as a peak current mode regulator control circuit, or in a second mode as a constant off-time time mode regulator control circuit.

TECHNICAL FIELD

The present disclosure relates generally to regulators, and moreparticularly voltage regulator control circuits, and to related circuitsand methods.

BACKGROUND INFORMATION

A DC-to-DC converter is a circuit that typically has a control loop ormultiple nested control loops. There are various types of control loopsand control loop architectures that can be employed. One class ofcontrol loop is the so-called current mode control loop. Within thegeneral class of current mode control loops, there are varioussubcategories including include peak, valley, average, hysteretic,constant on-time, constant off-time, and emulated current mode. Some ofthese control mode types may be more advantageous in certainapplications, whereas other control mode types may be more advantageousin other applications. The various control loop techniques havedifferent characteristics, which may translate into advantages anddisadvantages depending on the application.

SUMMARY

In a first novel aspect, a power converter circuit such as a DC-to-DCconverter includes a voltage regulator control integrated circuit. Thisvoltage regulator control integrated circuit is operable in a valleycurrent (VC) mode or in a current-mode constant on-time mode (CM-COT).In one example, the voltage regulator control integrated circuit isprogrammable and has a mode control conductor and a mode controlintegrated circuit terminal MODE. The term “operable” as it is used heremeans programmably operable in that the voltage regulator controlintegrated circuit has the circuitry to operate in both modes and can beeasily switched from operating in one mode to operating in the othermode, even though the mode control conductor and/or mode controlterminal may be hardwired or otherwise permanently connected so thatthat particular instance of the voltage regulator control integratedcircuit always operates in only one of the two modes.

The voltage regulator control integrated circuit includes a feedbackintegrated circuit terminal FB, a compensation integrated circuitterminal COMP, a switching integrated circuit terminal SW, a supplyinput voltage integrated circuit terminal VIN, a ground integratedcircuit terminal GND, a mode control integrated circuit terminal MODE,an error amplifier circuit, a comparator circuit, a compensation signalgenerator circuit, an oscillator/one-shot circuit, a latch, a currentsense circuit, an inverter, a high side switch HSS, and a low sideswitch LSS. In the VC mode, the compensation signal generator circuitoutputs a ramp signal, whereas in the CM-COT mode the compensationsignal generator circuit outputs an AC ground signal. In the VC mode,the oscillator/one-shot circuit outputs a free-running oscillatingsignal, whereas in the CM-COT mode the oscillator/one-shot circuitoutputs a delayed one-shot signal.

In the VC mode, the various parts of the voltage regulator controlintegrated circuit (including the error amplifier circuit, thecompensation signal generator circuit, the comparator circuit, thecurrent sense circuit, the oscillator/one-shot circuit, and the latch)are configured and are intercoupled in such a way that they operatetogether as a VC mode regulator control circuit. The overall DC-to-DCconverter therefore is controlled using a VC mode control loop.

In the CM-COT mode, the various parts of the voltage regulator controlintegrated circuit are configured and are intercoupled in such a waythat they operate together as a CM-COT mode regulator control circuit.The overall DC-to-DC converter therefore is controlled using a CM-COTmode control loop.

In a second novel aspect, a power converter circuit includes a voltageregulator control integrated circuit. This voltage regulator controlintegrated circuit is operable in a peak current mode or in acurrent-mode constant off-time mode. The voltage regulator controlintegrated circuit includes a feedback integrated circuit terminal FB, acompensation integrated circuit terminal COMP, a switching integratedcircuit terminal SW, a supply input voltage integrated circuit terminalVIN, a ground integrated circuit terminal GND, a mode control integratedcircuit terminal MODE, an error amplifier circuit, a comparator circuit,a compensation signal generator circuit, an oscillator/one-shot circuit,a latch, a current sense circuit, an inverter, a high side switch HSS,and a low side switch LSS. In the peak current mode, the compensationsignal generator circuit outputs a ramp signal, whereas in thecurrent-mode constant off-time mode the compensation signal generatorcircuit outputs an AC ground signal. In the peak current mode, theoscillator/one-shot circuit outputs a free-running oscillating signal,whereas in the current-mode constant off-time mode theoscillator/one-shot circuit outputs a delayed one-shot signal. As is thecase with the integrated circuit of the first novel aspect, a giveninstance of the integrated circuit of the second novel aspect may behardwired so that it only operates in one of the two modes. Otherinstances of the same integrated circuit design may then be hardwired sothat they only operate in the other of the two modes.

In the first and second novel aspect, although an example of the overallDC-to-DC converter is described in which there is a voltage regulatorcontrol integrated circuit, the control circuitry of the DC-to-DCconverter can also be implemented with separate components and/ormultiple different integrated circuits. Various subparts of the novelcontrol circuitry can be integrated and other subparts not. For example,a voltage regulator control integrated circuit as described above may beprovided, but the oscillator circuit may be located off chip. In oneexample, a voltage regulator control integrated circuit as describedabove is provided, but the current sense circuit is located off chip.The novel voltage regulator control circuit can also be implemented indiscrete form without any special integrated circuit.

The foregoing is a summary and thus contains, by necessity,simplifications, generalizations and omissions of detail; consequentlyis it appreciated that the summary is illustrative only. Still othermethods, and structures and details are set forth in the detaileddescription below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 is a circuit diagram of a circuit involving a novel voltageregulator control integrated circuit in accordance with a first novelaspect.

FIG. 2 is a waveform diagram that illustrates operation of the circuitof FIG. 2 when the voltage regulator control integrated circuit isoperating in the valley current mode.

FIG. 3 is a waveform diagram that illustrates operation of the circuitof FIG. 2 when the voltage regulator control integrated circuit isoperating in the current-mode constant on-time mode.

FIG. 4 is a circuit diagram of another example of a summing circuit of acomparator circuit.

FIG. 5 is a circuit diagram of an example of a compensation signalgenerator circuit.

FIG. 6 is a waveform diagram of waveforms of the OSC signal in thecircuit of FIG. 5, and the ramp signal V_(C) as output by the circuit ofFIG. 5.

FIG. 7 is a circuit diagram of another example of a current sensecircuit.

FIG. 8 is a circuit diagram of another example of a current sensecircuit.

FIG. 9 is a circuit diagram of another example of a current sensecircuit.

FIG. 10 is a circuit diagram that illustrates how the summing circuit ofFIG. 4 can be disposed in the V_(CURRENT) signal path into thenon-inverting input lead of a comparator.

FIG. 11 is a circuit diagram of another example of a osc/one-shotcircuit.

FIG. 12 is a circuit diagram that illustrates another way that thesequential logic element may be coupled to receive the set signal from acomparator circuit and to receive the reset signal from an osc/one-shotcircuit.

FIG. 13 is a circuit diagram of a DC-to-DC voltage converter circuit inaccordance with a second novel aspect in which the circuit is operablein either a peak current mode or in a current-mode constant off-timemode.

FIG. 14 is a waveform diagram that illustrates operation of the circuitof FIG. 13 in the peak current mode.

FIG. 15 is a waveform diagram that illustrates operation of the circuitof FIG. 13 in the current-mode constant off-time mode.

DETAILED DESCRIPTION

FIG. 1 is a diagram of a DC-to-DC voltage converter circuit 1 inaccordance with a first novel aspect. Circuit 1 includes a voltageregulator control integrated circuit 2, an inductor 3, an outputcapacitor 4, feedback voltage divider resistors 5 and 6, and an externalcompensation capacitor 7. Voltage regulator control integrated circuit 2includes a feedback integrated circuit terminal FB 8, a compensationintegrated circuit terminal COMP 9, an switching integrated circuitterminal SW 10, a supply input voltage integrated circuit terminal VIN11, a ground integrated circuit terminal GND 12, a mode controlintegrated circuit terminal MODE 13, an error amplifier circuit 14, acomparator circuit 15, a compensation signal generator circuit 16, anoscillator/one-shot circuit 17, a latch 18, a current sense circuit 19,an inverter 20, a high side switch HSS 21, and a low side switch LSS 22.

The voltage regulator control integrated circuit 2 is actually packagedin an integrated circuit package (not shown) that has a set ofintegrated circuit package terminals (not shown). In this example, thereis a one-to-one correspondence between the integrated circuit terminals8-13 shown and the corresponding integrated circuit package terminals.It is the integrated circuit package terminals that actually couple mostdirectly to the external components 3-7. The external components 3-7 aretypically soldered, along with the packaged voltage regulator controlintegrated circuit, on a printed circuit board (not shown). Forsimplicity of explanation, the extra connections of the package betweenthe integrated circuit terminals and the external components are omittedfrom the description and explanation below, but it is understood thatthese connections and structures exist.

Error amplifier circuit 14 includes a differential transconductanceamplifier 23, a voltage reference generator 24, and a compensationresistor R_(COMP) 25. Compensation resistor R_(COMP) 25 and externalcompensation capacitor C_(COMP) 7 together form an RC compensationnetwork that is coupled to the output lead 29 of amplifier 23. Thevoltage reference generator 24 supplies a 1.2 volt reference voltageonto the non-inverting input lead 26 of amplifier 23. The invertinginput lead 27 of amplifier is coupled to the feedback integrated circuitterminal FB 8. A fraction of the output voltage V_(OUT) on node 28 issupplied by the voltage divider involving resistors 5 and 6 onto thefeedback integrated circuit terminal FB 8, and to the inverting inputlead 27 of amplifier 23. The error amplifier circuit 14 supplies anerror voltage signal V_(E) to the summing circuit 30 of the comparatorcircuit 15.

Compensation signal generator circuit 16 includes a compensation signalgenerator circuit 31 and a switch SW1 32. The compensation signalgenerator circuit 16 supplies a compensation voltage signal V_(C) to thesumming circuit 30 of the comparator circuit 15. Compensation signalgenerator 31 supplies a ramp voltage signal via conductor 33 to switchSW1 32. The overall circuit 1 is operable in a valley current (VC) modeand in a current-mode constant on-time (CM-COT) mode. For brevityreasons, the CM-COT mode may sometimes be denoted the COT mode in thedescription below. In the VC mode, the switch SW1 32 is in the “A”position. The switch SW1 32 therefore couples the ramp voltage signal asoutput by the compensation signal generator circuit 16 onto the switchoutput node 34. The compensation voltage signal V_(C) is therefore theramp signal when the circuit is in the VC mode. In the COT mode, theswitch SW1 32 is in the “B” position. The switch SW1 32 thereforecouples a ground conductor 35 to the switch output node. Thecompensation voltage signal V_(C) is therefore ground potential when thecircuit is in the COT mode. The potential on ground conductor 35 is alsomore generally referred to as an AC ground signal.

Comparator circuit 15 includes the summing circuit 30 and a differentialcomparator 36. The summing circuit 30 receives the error voltage signalV_(E) from the error amplifier circuit 14 and receives the compensationvoltage signal V_(C) from the compensation signal generator circuit 16,and supplies an error and compensated error voltage signal V_(E-C) ontothe non-inverting input lead 37 of comparator 36. This signal V_(E-C) isalso referred to as the compensated error signal V_(E-C). The currentsense circuit 19 outputs a voltage signal V_(CURRENT) whose magnitude isindicative of a magnitude of a current SW. This current SW is flowingfrom switching node SW 38 and through integrated circuit terminal SW 10and then through the external inductor 3. The voltage signal V_(CURRENT)is supplied by the current sense circuit 19 onto the non-inverting inputlead 39 of comparator 36. Comparator 36 supplies a set signal SET ontothe set input lead of the latch 18.

The current sense circuit 19 is illustrated in general schematic form.The actual current sense circuit and circuitry can take one of severaldifferent suitable forms. For example, the current sense circuit 19 caninclude a sense resistor that is disposed in the current path of the SWcurrent, and the voltage drop across this sense resistor can be obtainedand converted into the voltage signal V_(CURRENT). For example, thecurrent sense circuit 19 can include a current mirror that mirrors theSW current, and this mirror current can in turn be converted into thevoltage signal V_(CURRENT). Actual current flow between the switchingnode SW 38 and the integrated circuit terminal SW 10 need not be senseddirectly, but rather another voltage or signal can be sensed that isindicative of the magnitude of the current SW. For example, one of thehigh side switch HSS 21 and low side switch LSS 22 may be a transistorthat has a companion smaller current mirror transistor, and the currentflow through this companion current mirror transistor can be sensed andconverted into the voltage signal V_(CURRENT).

Osc/one-shot circuit 17 includes an oscillator circuit 40, a delay andone-shot circuit 41, and a switch 42. Osc/one-shot circuit 17 supplies areset signal RESET onto the reset input lead of the latch 18.

When the overall circuit is operating in the valley current (VC) mode,the switch 42 is switched to the “A” position so that it couples a fixedfrequency free-running oscillating signal OSC as output from theoscillator 40 onto the switch output node 43. The reset signal RESET istherefore the free-running oscillating signal OSC when the circuit is inthe VC mode. The free-running oscillating signal OSC is a pulse train ofnarrow pulses. The period of the oscillating signal OSC is onemicrosecond. The oscillating signal OSC is also supplied via conductor44 to the compensation signal generator 31 so that pulses of theoscillating signal will initiate voltage ramps of the ramp signal asoutput by the compensation signal generator 31. A rising edge of theoscillating signal OSC causes the compensation signal generator 31 tooutput a voltage ramp. For the first five nanoseconds, the voltage levelof the ramp signal starts at zero volts and does not change, but thenafter the initial five nanosecond period the voltage of the ramp signalincreases at a rate of 100 kV per second.

When the overall circuit is operating in the constant on-time (COT)mode, the switch 42 is switched to the “B” position so that it couples adelayed one-shot pulse signal as output by the delay and one-shotcircuit 41 onto the switch output node 43. The reset signal RESET istherefore the delayed one-shot pulse signal when the circuit is in theCOT mode. The delay and one-shot circuit 41 detects rising edges of theswitch control signal SWC as output by latch 18. If the delay andone-shot circuit 41 detects a rising edge, then after a “fixed delaytime” (from the rising edge) it outputs one high pulse. The high pulseis also of a fixed predetermined duration. All such high pulses outputby circuit 41 are of the same fixed predetermined duration. The term“fixed delay time” as it is used here means fixed from the perspectiveof the control loop, but the fixed delay time is selected using a lookuptable. Based on: 1) a desired target output voltage V_(OUT), 2) themagnitude of the input voltage VIN, 3) the current operating temperatureof the integrated circuit, and 4) the target operating switchingfrequency, the lookup table outputs a digital value that in turn setsthe fixed delay time. The term “constant” in the larger term “constanton-time control mode” refers to the fact that this delay time is“fixed”, as the “delayed one-shot pulse” signal is output by the delayand one-shot circuit 41.

Latch 18 is a digital SR latch. The switch control signal SWC as outputby the latch 18 is a digital signal. When the switch control signal SWCis at a digital logic high level, the high side switch HSS 21 is on andconductive. The low side switch LSS 22 is off and non-conductive due tothe inverter 20 inverting the control signal for the low side switch.When the switch control signal SWC is at a digital logic low level, thelow side switch LSS 22 is on and conductive and the high side switch HSS21 is off and non-conductive. The high side and low side switches areillustrated in general schematic form. There are various ways ofimplementing these switches. In one example, both the switches HSS 21and LSS 22 are N-channel field effect transistors. There are severalsuitable gate drive and bootstrap circuits for driving thesetransistors. This circuitry is conventional and is not illustrated.

FIG. 2 is a waveform diagram that illustrates operation of the circuit 1of FIG. 1 in the valley current (VC) mode. When the circuit 1 isoperating in the VC mode, the switches SW1 and SW2 are both set to the“A” position. The beginning of a high pulse of the oscillating signalOSC resets the latch 18, thereby causing the switch control signal SWCto transition from a digital logic high to a digital logic low. The lowside switch LSS 22 turns on, and the current SW begins to decrease. Thevoltage signal V_(CURRENT) therefore begins to decrease. When thedecreasing voltage signal V_(CURRENT) crosses the error and compensatederror voltage signal V_(E-C) then the comparator circuit 15 asserts theset signal SET to a digital logic high. This sets the latch 18, andturns off the low side switch LSS 22 and turns on the high side switchHSS 21. The voltage signal V_(CURRENT) then starts to increase again.The voltage signal V_(CURRENT) increases until the next rising edge ofthe oscillating signal OSC. The period of time between successive risingedges of the oscillating signal OSC is fixed from cycle to cycle. Theduty cycle is determined by the amount of time required, after the latch18 is reset, for the decreasing voltage signal V_(CURRENT) to cross thecompensated error signal V_(E-C). This is called “valley current mode”control because the signal V_(E-C) causes the latch to be set in a“valley” of the V_(CURRENT) signal.

FIG. 3 is a waveform diagram that illustrates operation of the circuit 1of FIG. 1 in the current-mode constant on-time (COT) mode. In the fifthwaveform down from the top of the diagram, the V_(E) and V_(E-C) signalshave the same, or almost exactly the same, waveform. When the circuit 1is operating in the COT mode, the switches SW1 and SW2 are both set tothe “B” position. When the high side switch 21 is on, it is on for apre-defined fixed amount of time. This amount of time is set by the“delay time” of the delay and one-shot circuit 41. The on/off duty-cycleof the high side switch HSS 21 is regulated by changing the off time ofthe high side switch HSS 21. When the low side switch LSS 22 is turnedon at the end of an on time of the high side switch HSS 21, the voltagesignal V_(CURRENT) begins decreasing. When the magnitude of V_(CURRENT)decreases to the point that it reaches the magnitude of the compensatederror voltage signal V_(E-C) then the comparator circuit 15 switches andasserts the set signal SET high. This sets the latch 18, and causes theswitch control signal SWC to transition from a digital logic low to adigital logic high. The amount of time that the high side switch HSS 21was off is what adjusts the on/off duty-cycle. The low to hightransition of the switch control signal SWC turn on the high side switchHSS 21 and starts the next on time of the high side switch HSS 21. Afteranother fixed amount of “delay time”, as determined by the “delay time”of the delay and one-shot circuit 41, the delay and one-shot circuit 41outputs a high pulse. Due to switch SW2 being set to the “B” position,this beginning of this high pulse is conducted onto the reset input oflatch 18. The beginning of this high pulse causes the latch 18 to reset,and causes the high side switch HSS 21 to be turned off. Due to theinner wideband current control loop involving current sense circuit 19,this constant on-time control mode is called a “current-mode constanton-time” (CM-COT) control mode.

Although an example of the voltage regulator control integrated circuit2 is set forth above that has a mode control integrated circuit terminalMODE 13, in another example there is no mode control integrated circuitterminal MODE 13. Rather, the digital logic value on the internal modecontrol conductor 45 is hardwired or otherwise set on-chip. An antifuse,an EEPROM element, a flash memory element, a mask programmable element,or a one-time programmable (OTP) element can be provided on-chip to setthe digital logic value on conductor 45. In another example, the modecontrol integrated circuit terminal MODE 13 is provided, but it is notbonded out to a package terminal. Rather, bond wires disposed entirelywithin the integrated circuit package couple either a digital logic highvoltage or a digital logic low voltage onto the MODE terminal 13. Thesemiconductor device manufacturer may produce one type of voltageregulator control integrated circuit, with some instances of thosevoltage regulator control integrated circuits being hardwired or presetto function in the VC mode, and with other instances of those voltageregulator control integrated circuits being hardwired or preset tofunction in the COT mode. Customers wanting voltage regulator controlintegrated circuits employing both types of control modes can besatisfied by the semiconductor device manufacturer with a single voltageregulator control integrated circuit design.

Although the particular embodiment of the voltage regulator integratedcircuit of FIG. 1 involves a compensation signal generator circuit, inanother embodiment the voltage regulator integrated circuit isprogrammably operable to operate in either the COT mode or the VC modebut yet it does not have a compensation signal generator circuit. If thedesired target output voltage V_(OUT) is greater than one half magnitudeof the input voltage V_(IN), then the integrated circuit need not have avoltage regulator compensation signal generator circuit. No switch SW132 and no summing circuit 30 are therefore required either. Accordingly,in one embodiment the voltage regulator integrated circuit is lessversatile but it also does not have any voltage regulator compensationsignal generator circuit, any switch SW1 32, or any summing circuit 30.Although an embodiment of the voltage regulator integrated circuit isdescribed above that has both a high side switch HSS and a low sideswitch LSS, in another embodiment there is no low side switch LSS.Rather, a diode is disposed in the place of the low side switch LSSillustrated in FIG. 1. The cathode of the diode is coupled to switchingnode SW 38, and the anode of the diode is coupled to the ground node andconductor.

Although an embodiment of the voltage regulator integrated circuit isdescribed above in which the switching current SW flowing on theintegrated circuit is detected, or a part of this current SW isdetected, in another embodiment no such switching current or portionthereof is detected, either directly or indirectly. Rather, anothercircuit is provided on the integrated circuit, and this other circuitgenerates a separate current, where this separate current emulates, or“mimics”, the switching current SW. This other separate current is thendetected and converted into the V_(CURRENT) signal. The V_(CURRENT)signal is still indicative of the magnitude of the switching current SW,but the V_(CURRENT) signal is generated without measuring any part ofthe switching current SW, either directly or indirectly.

Although an example of the voltage regulator integrated circuit isdescribed above in which the error signal voltage signal V_(E) issupplied the comparator circuit 15 on one conductor, and the compensatederror voltage signal V_(E-C) is present on the other side of the summingcircuit 30 on a different conductor, in another example the errorvoltage signal V_(E) is supplied to the comparator circuit 15 via aconductor, and the compensation voltage signal V_(C) is made tocompensate the error signal on that node and conductor such that it addsto the error voltage signal present on that same node and conductor, andthereby causes the resulting compensated error voltage signal V_(E-C)also to be simultaneously present on the same node and conductor. Thesignals V_(E) and V_(E-C) are simultaneously present on the same singleconductor, and this single conductor extends from the error amplifiercircuit 14 all the way to the non-inverting input lead 37 of comparator36. Although the signals V_(E) and V_(E-C) are not present on twodifferent conductors in this example, the signal V_(C) is present on adifferent conductor (namely, on the conductor that extends out of thecompensation signal generator circuit 16).

Although an integrated circuit implementation of the regulator controlportion of the circuit 1 of FIG. 1 is shown above, in other examples theregulator control portion is not implemented on an integrated circuitbut rather is a printed circuit board level circuit. Although a specificexample is set forth above involving a latch, the function of the latchcan be performed by another type of sequential logic element (forexample, a flip-flop) more generally. A condition of a given voltagelevel being stored on a particular storage node within the sequentiallogic element can be referred to as either the set state, or the resetstate. The terms set and reset in this context are relative.

Although an example of the voltage regulator control integrated circuit2 is described above as including the high side switch HSS 21 and thelow side switch LSS 22, in other examples of the voltage regulatorcontrol integrated circuit these switches are disposed outside theintegrated circuit. The voltage regulator control integrated circuit 2may include a high side driver circuit for driving the gate of anexternal high side N-channel field effect transistor, and may alsoinclude a low side driver circuit for driving the gate of an externallow side N-channel field effect transistor. Alternatively, the switchcontrol signal SWC and/or its complement can be made to exit the voltageregulator control integrated circuit without any gate driver circuitsbeing built into the integrated circuit.

FIG. 4 is a diagram of another example of the summing circuit 30 of thecomparator circuit 15. The error amplifier circuit 14 supplies the errorvoltage signal V_(E) to the comparator circuit 15 on the non-invertinginput lead 37 of the comparator 36. The compensation signal generatorcircuit 16 supplies the compensation voltage signal V_(C) to thecomparator circuit 15 onto the input lead of buffer 46.

FIG. 5 is a diagram of an example of compensation signal generator 31.

FIG. 6 is a waveform diagram of waveforms of the OSC signal in thecircuit of FIG. 5, and the ramp signal V_(C) as output by the circuit ofFIG. 5.

FIG. 7 is a diagram of another example of the current sense circuit 19.This circuit 19 does not directly measure any current, but rather itemploys a matched RC network 47 to detect changes across the inductor 3.Voltage changes across the capacitor of the RC network are detected bythe transconductance amplifier 48. Resistor 49 is used to convert thecurrent signal as output by the transconductance amplifier 48 into thevoltage signal V_(CURRENT).

FIG. 8 is a diagram of another example of the current sense circuit 19.

FIG. 9 is a diagram of another example of current sense circuit 19. Thiscircuit 19 employs a current sense resistor 51. The voltage drop acrossthis current sense resistor is detected by the transconductanceamplifier 52 and resistor 53. The resulting voltage signal V_(CURRENT)is indicative of current flow if the sense resistor is disposed in thepath of the current SW flowing through inductor 3. The current senseresistor can be disposed in the current path either on the regulatorside of the inductor 3, or it can be disposed in the current pathbetween the inductor 3 and the output capacitor 4. Alternatively, thesense resistor can be disposed in the current path between the high sidevoltage node and the point labeled 38 in FIG. 1 so that the currentbeing sensed is current flow through the high side switch HSS 21. Thesense resistor can be disposed between the high side voltage node andthe HSS switch 21. The sense resistor can also be disposed between theHSS switch 21 to the point 38. Alternatively, the sense resistor can bedisposed in the current path between the point 38 and the low sidevoltage node so that the current being sensed is current flow throughthe low side switch LSS 22. The sense resistor can be disposed betweenthe low side voltage node and the LSS switch 22. The sense resistor canalso be disposed between the LSS switch 22 to the point 38. In all thesecases, the resulting voltage signal V_(CURRENT) is indicative of amagnitude of a current and is suitable for use in the current controlloop.

FIG. 10 is a diagram that illustrates how the summing circuit 30 can bedisposed in the V_(CURRENT) signal path into the non-inverting inputlead 39 of comparator 36. In this case, the ramp signal as generated bycircuit 31 is inverted as compared to the ramp signal in the example ofFIG. 1. The ramp signal used in FIG. 10 has a sawtooth wave shape. Eachtooth of the sawtooth ramp signal has a negative slope as illustrated inblock 31 of FIG. 10.

FIG. 11 is a diagram of another example of the osc/one-shot circuit 17.In this case, there is no switch SW2, but rather the two circuits 41 and40 have enable input leads. If one of these circuits is not enabled,then that circuit outputs a digital logic low signal. Due to inverter54, only one of the two circuits 40 and 41 is enabled at a given time.The signal from that enabled circuit passes through OR gate 55 and issupplied as the reset signal to the latch 18.

FIG. 12 is a diagram that illustrates another way the sequential logicelement may be coupled to receive the set signal from the comparatorcircuit 15 and to receive the reset signal from the osc/one-shot circuit17. The logic employed by the sequential logic element in this case isinverted so that the set signal is supplied onto what is called thereset input lead of the sequential logic element, and so that the resetsignal is supplied onto what is called the set input lead of thesequential logic element. The signal that is output from the sequentiallogic element is therefore in the inverted form. Accordingly, ratherthan placing the inverter 20 in the signal path to the low side switchLSS 22 as in the case of FIG. 1, the inverter 20 is placed in the signalpath to the high side switch HSS 21. Alternatively, the same polarity ofswitching control signal as is shown in FIG. 1 can be output from thesequential logic element by outputting the switching control signal fromthe inverted data output lead of the sequential logic element.Functionally, what is labeled as the reset input lead of the sequentiallogic element is performing the function of receiving the SET signal. Itis therefore functionally putting the sequential logic element into theset state. What is labeled as the set input lead of the sequential logicelement is performing the function of receiving the RESET signal. It istherefore functionally putting the sequential logic element into thereset state.

FIG. 13 is a circuit diagram of a DC-to-DC voltage converter circuit 201in accordance with a second novel aspect. In the circuit of FIG. 13, thevoltage regulator control integrated circuit 202 is like the voltageregulator control integrated circuit 2 of FIG. 1, except that thisvoltage regulator control integrated circuit 202 is operable in aselectable one of either a peak current mode or a current-mode constantoff-time mode. If the switches SW1 and SW2 are in the “A” position thenthe converter circuit 201 operates in the peak current (PC) controlmode, whereas if the switches SW1 and SW2 are in the “B” position thenthe converter circuit 201 operates in the current-mode constant off-timecontrol mode. The contents of like numbered circuit components in thetwo diagrams are the same as described above in connection with FIG. 1,except for the compensation signal generator circuit block 31. Thecompensation signal generator circuit block 31 of FIG. 13 generates aramp signal that has a sawtooth wave shape, with each tooth having adownward slope. The ramp of the tooth starts at zero volts, and thendecreases with a constant negative slope downward to about minus fiftymillivolts. This sawtooth wave shape is illustrated schematically in theblock 31 of FIG. 13. The comparator 36 is the same circuit as in FIG. 1,except that the V_(CURRENT) signal is supplied onto the non-invertinginput lead and the V_(E-C) signal is supplied onto the inverting inputlead. The comparator 36 supplies the RESET signal onto the reset inputlead of the latch 18, whereas the osc/one-shot circuit 17 supplies theSET signal onto the set input lead of the latch 18. The signal that isoutput from the inverted Q data output of the latch 18 is used totrigger the delay and one-shot circuit 41.

Although the specific example of the DC-to-DC voltage converter circuit201 of FIG. 13 involves a ramp signal that has sawtooth wave shape, witheach tooth having a downward slope, the same technique explained abovein connection with FIG. 10 can be applied to the converter circuit 201of FIG. 13. A ramp signal that has a sawtooth wave shape, with eachtooth having a positive slope, can be employed by moving the location ofthe summing circuit 30 of FIG. 13 from being in the signal path into theinverting input lead 39 so that it is then in the signal path into thenon-inverting input lead 37. Also, as explained above in connection withFIG. 12, the signal as output from comparator 36 can be supplied ontothe set input lead of the latch 18, and the signal as output by theosc/one-shot circuit 17 can be supplied onto the reset input lead of thelatch 18. In that case the data output signals as output from the latch18 would be inverted (as compared to what is shown in FIG. 13), so thesesignals should be inverted again before they are used to controlswitches, or to trigger the one-shot. The techniques and circuits ofFIGS. 4-12 can be employed to realize the DC-to-DC voltage convertercircuit 201 of FIG. 13 in different ways.

FIG. 14 is a waveform diagram that that illustrates operation of thecircuit 201 of FIG. 13 in the peak current mode. When the risingV_(CURRENT) crosses the compensated error signal V_(E-C) then thecomparator circuit 15 asserts the RESET signal to a digital logic highand causes the sequential logic element 18 to be reset.

FIG. 15 is a waveform diagram that that illustrates operation of thecircuit 201 of FIG. 13 in the current-mode constant off-time mode. Whenthe sequential logic element 18 is in the reset state, then the highside switch HSS 21 is off. This is the so-called “off time”. When thesequential logic element 18 is reset, then the delay and one-shotcircuit 41 is triggered. After a constant amount of “time delay”, thedelay and one-shot circuit 41 outputs a high pulse. The rising edge ofthis high pulse passes through the switch SW2 and sets the sequentiallogic element 18. The “time delay” is constant from period to period.This control mode therefore is a “constant off-time” control mode. It isa “current-mode” constant off-time control mode due to the innerwideband current control loop involving current sense circuit 19.

Although certain specific embodiments are described above forinstructional purposes, the teachings of this patent document havegeneral applicability and are not limited to the specific embodimentsdescribed above. Accordingly, various modifications, adaptations, andcombinations of various features of the described embodiments can bepracticed without departing from the scope of the invention as set forthin the claims.

1. A voltage regulator control integrated circuit having a valleycurrent (VC) mode and a constant on-time (COT) mode, the voltageregulator control integrated circuit comprising: a sequential logicelement having a set input lead, a reset input lead, and an output lead;a comparator circuit that supplies a set signal SET to the sequentiallogic element; a osc/one-shot circuit that supplies a reset signal RESETto the sequential logic element, wherein in the COT mode the resetsignal RESET is a delayed one-shot pulse signal, and wherein in the VCmode the reset signal RESET is a free-running oscillating signal; acompensation signal generator circuit that supplies a compensationvoltage signal V_(C) to the comparator circuit, wherein in the COT modethe compensation voltage signal V_(C) is an AC ground signal, andwherein in the VC mode the compensation voltage signal V_(C) is a rampsignal; a current sense circuit that outputs a voltage signalV_(CURRENT) indicative of a magnitude of a current, wherein the currentsense circuit supplies the voltage signal V_(CURRENT) to the comparatorcircuit; and an error amplifier circuit that supplies an error voltagesignal V_(E) to the comparator circuit.
 2. The voltage regulator controlintegrated circuit of claim 1, further comprising: a mode controlintegrated circuit terminal MODE, wherein a signal received on the modecontrol integrated circuit terminal MODE determines whether the voltageregulator control integrated circuit operates in the COT mode or in theVC mode.
 3. The voltage regulator control integrated circuit of claim 1,wherein the voltage regulator control integrated circuit is hardwired sothat it only operates in one of the COT mode and the VC mode.
 4. Thevoltage regulator control integrated circuit of claim 1, wherein thecomparator circuit generates an error and compensated error voltagesignal V_(E-C) by summing the error voltage signal V_(E) and thecompensation voltage signal V_(C), wherein the comparator circuitcomprises a comparator, wherein the error and compensated error voltagesignal V_(E-C) is supplied onto a first input lead of the comparator,and wherein the voltage signal V_(CURRENT) is supplied onto a secondinput lead of the comparator.
 5. The voltage regulator controlintegrated circuit of claim 1, wherein the current is a current flowingon the integrated circuit.
 6. The voltage regulator control integratedcircuit of claim 5, wherein the current sense circuit comprises acircuit element taken from the group consisting of: a current senseresistor, a current mirror transistor, and a matched RC network.
 7. Thevoltage regulator control integrated circuit of claim 1, wherein theerror amplifier circuit comprises a reference voltage generator, adifferential transconductance amplifier, and a compensation resistor,wherein the reference voltage generator is coupled to a first input leadof the differential transconductance amplifier, and wherein thecompensation resistor is coupled to an output lead of the differentialtransconductance amplifier.
 8. The voltage regulator control integratedcircuit of claim 7, further comprising: a feedback integrated circuitterminal FB, wherein a second input lead of the differentialtransconductance amplifier is coupled to receive a feedback signal fromthe feedback integrated circuit terminal FB.
 9. The voltage regulatorcontrol integrated circuit of claim 1, wherein the compensation signalgenerator circuit is coupled to receive the free-running oscillatingsignal from the osc/one-shot circuit.
 10. A voltage regulator controlintegrated circuit having a valley current (VC) mode and a constanton-time (COT) mode, the voltage regulator control integrated circuitcomprising: a sequential logic element having a set input lead, a resetinput lead, and an output lead; a comparator circuit that supplies a setsignal SET to the sequential logic element; a osc/one-shot circuit thatsupplies a reset signal RESET to the sequential logic element, whereinin the COT mode the reset signal RESET is a delayed one-shot pulsesignal, and wherein in the VC mode the reset signal RESET is afree-running oscillating signal; a compensation signal generator circuitthat supplies a compensation voltage signal V_(C) to the comparatorcircuit, wherein in the COT mode the compensation voltage signal V_(C)is an AC ground signal, and wherein in the VC mode the compensationvoltage signal V_(C) is a ramp signal; a current sense circuit thatoutputs a voltage signal V_(CURRENT) indicative of a magnitude of acurrent, wherein the current sense circuit supplies the voltage signalV_(CURRENT) to the comparator circuit; and an error amplifier circuitthat supplies an error voltage signal V_(E) to the comparator circuit,wherein the compensation signal generator circuit comprises a rampsignal generator and a switch, wherein in the VC mode the switch isswitched to receive the ramp signal from the ramp signal generator andto output the ramp signal onto a switch output node, and wherein in theCOT mode the switch is switched to couple the switch output node to anAC ground node.
 11. A voltage regulator control integrated circuithaving a valley current (VC) mode and a constant on-time (COT) mode, thevoltage regulator control integrated circuit comprising: a sequentiallogic element having a set input lead, a reset input lead, and an outputlead; a comparator circuit that supplies a set signal SET to thesequential logic element; a osc/one-shot circuit that supplies a resetsignal RESET to the sequential logic element, wherein in the COT modethe reset signal RESET is a delayed one-shot pulse signal, and whereinin the VC mode the reset signal RESET is a free-running oscillatingsignal; a compensation signal generator circuit that supplies acompensation voltage signal V_(C) to the comparator circuit, wherein inthe COT mode the compensation voltage signal V_(C) is an AC groundsignal, and wherein in the VC mode the compensation voltage signal V_(C)is a ramp signal; a current sense circuit that outputs a voltage signalV_(CURRENT) indicative of a magnitude of a current, wherein the currentsense circuit supplies the voltage signal V_(CURRENT) to the comparatorcircuit; and an error amplifier circuit that supplies an error voltagesignal V_(E) to the comparator circuit, wherein the osc/one-shot circuitcomprises a one-shot circuit, an oscillator, and a switch, wherein inthe VC mode the switch is switched to receive the free-runningoscillating signal from the oscillator and to output the free-runningoscillating signal onto a switch output node, and wherein in the COTmode the switch is switched to receive a delayed one-shot pulse signalfrom the one-shot circuit and to output the delayed one-shot pulsesignal onto the switch output node.
 12. The voltage regulator controlintegrated circuit of claim 1, further comprising: a high side switchHSS, wherein the high side switch HSS is operable to close and to supplya high side voltage onto a switching node SW; and a low side switch LSS,wherein the low side switch LSS is operable to close and to supply a lowside voltage onto the switching node SW.
 13. The voltage regulatorcontrol integrated circuit of claim 12, further comprising: a switchingoutput integrated circuit terminal SW, wherein the switching outputintegrated circuit terminal SW is a part of the switching node SW. 14.The voltage regulator control integrated circuit of claim 1, furthercomprising: a switching output integrated circuit terminal SW, whereinthe sequential logic element outputs a switching output signal from thevoltage regulator control integrated circuit via the switching outputintegrated circuit terminal SW.
 15. An integrated circuit having avalley current (VC) mode and a constant on-time (COT) mode, theintegrated circuit comprising: an error amplifier circuit adapted toreceive a feedback signal FB; a compensation signal generator circuitadapted to output a compensation voltage signal V_(C), wherein thecompensation voltage signal V_(C) is one of a ramp signal and an ACground signal; a comparator circuit adapted to receive an error voltagesignal V_(E) from the error amplifier circuit, and adapted to receivethe compensation voltage signal V_(C) from the compensation signalgenerator circuit; a osc/one-shot circuit adapted to output a resetsignal RESET, wherein the reset signal RESET is one of a free-runningoscillating signal and a delayed one-shot pulse signal; and a sequentiallogic element adapted to receive a set signal SET from the comparatorcircuit and adapted to receive the reset signal RESET from theosc/one-shot circuit, wherein the sequential logic element outputs aswitch control signal SWC, wherein in the COT mode the integrated erroramplifier circuit, the compensation signal generator circuit, thecomparator circuit, the osc/one-shot circuit, and the sequential logicelement are configured to operate together as a COT mode regulatorcontrol circuit, and in the VC mode the integrated error amplifiercircuit, the compensation signal generator circuit, the comparatorcircuit, the osc/one-shot circuit, and the sequential logic element areconfigured to operate together as a VC mode regulator control circuit.16. The integrated circuit of claim 15, further comprising: a modecontrol integrated circuit terminal MODE, wherein a signal received onthe mode control integrated circuit terminal MODE determines whether theintegrated circuit operates in the COT mode or in the VC mode.
 17. Theintegrated circuit of claim 15, wherein the integrated circuit ishardwired so that it only operates in one of the COT mode and the VCmode.
 18. The integrated circuit of claim 15, wherein the RESET signalis the free-running oscillating signal if the integrated circuit isoperating in the VC mode, and wherein the RESET signal is the delayedone-shot pulse signal if the integrated circuit is operating in the COTmode.
 19. The integrated circuit of claim 15, wherein the integratedcircuit is hardwired to operate in the COT mode, and wherein a rampsignal generator of the compensation signal generator circuit isdisabled.
 20. The integrated circuit of claim 15, wherein the integratedcircuit is hardwired to operate in the VC mode, and wherein a one-shotcircuit of the osc/one-shot circuit is disabled.
 21. A voltage regulatorcontrol circuit having a valley current (VC) mode and a constant on-time(COT) mode, the voltage regulator control circuit comprising: asequential logic element that has a set state and a reset state; acomparator circuit that supplies a set signal SET to the sequentiallogic element; a osc/one-shot circuit that supplies a reset signal RESETto the sequential logic element, wherein in the COT mode the resetsignal RESET is a delayed one-shot pulse signal, and wherein in the VCmode the reset signal RESET is a free-running oscillating signal; acompensation signal generator circuit that supplies a compensationvoltage signal V_(C) to the comparator circuit, wherein in the COT modethe compensation voltage signal V_(C) is an AC ground signal, andwherein in the VC mode the compensation voltage signal V_(C) is a rampsignal; a current sense circuit that outputs a voltage signalV_(CURRENT) indicative of a magnitude of a current, wherein the currentsense circuit supplies the voltage signal V_(CURRENT) to the comparatorcircuit; and an error amplifier circuit that supplies an error voltagesignal V_(E) to the comparator circuit. 22-42. (canceled)